The rule is called the Look Back Rule, but it really has nothing to do with the pitcher looking the runner back. If the ball is in the circle in the pitchers control a base runner is allowed to round a bag, but she must immediately proceed to one bag or the other, So she can stop but she must immediately run toward the next base or return to the one she just rounded. If the pitcher attempts to make a play on her, the look back rule no longer applies. The runner on third can also be off the bag but must make the same choice once the ball is in the circle under the pitchers control, (and the batter has made it to first base) either immediately continue home, or retreat back to third.
Umpires who call girls out for simply rounding the bag on a walk don't understand the rule.
Look Back is simply the name that has been applied to the rule, it has absolutely nothing to do with the pitcher "looking back" the runner. On a walk the rule is not in effect until the batter/runner reaches 1st base. If for any reason they stop at 1st, they must stay there, but, they are perfectly legal to round the base and stop. However, if no play is being made on them by the pitcher, they must then decide to either advance or return to 1st. Once they move they must continue non stop that direction unless the pitcher attempts to make a play on them.
If you are seeing players being called out for rounding and stopping, then the umpires apparently do not understand the rule or have been taught incorrectly.
Everything hinges on whether the pitcher has the ball inside the circle or not. To advance towards the next base, even only one step and then stop when pitcher has ball... br is out. This is called a waffle. Additional base runners are irrelevant.